docs: def is_parent_of(self, parent, child):
          """Return whether ``child`` is a branch descended from ``parent`` at
          any remove.
  
          """
          if parent == 'trunk':
              return True
          if child == 'trunk':
              return False
          if child not in self._branches:
              raise ValueError(
                  "The branch {} seems not to have ever been created".format(
                      child
                  )
              )
          if self._branches[child][0] == parent:
              return True
          return self.is_parent_of(parent, self._branches[child][0])